In his Bunker Archeology (1975), Paul Virilio establishes an inventory of bunker typologies and tries to determine what the essence of those militaries architecture might be.
The plans and sections inserted in the book illustrate spaces which are not anymore framed by walls as usual but rather spaces within the walls. The interior space is thus felt like tunnels and cavities inside a concrete mass, the wall itself.
However those walls have an important characteristics which is that they are not anchored in the ground, allowing themselves to slightly move whenever a bombshell explode nearby.
You can also read the two articles (here and here) we already released on boiteaoutils and the one written by Geoff Manaugh for BLDGBLOG.